ISPmanager, why is mail buggy?

Question

Email

Only yesterday it worked fine, but today I can’t send letters from either of the two mailboxes - it displays the same message (in the mail client):

Server response: )/ virtuser_508… Unbalanced ')'

I tried to reconnect the SMTP service, mailboxes - it's useless. The poison didn't help...
Here's what's in the admin panel:

I guess that something is wrong here, but what - there is not enough experience.

Answer 1

)/ virtuser_508… Unbalanced ')'
Somewhere there is an extra closing bracket or there is not enough opening bracket. Where exactly, without full logs it is not clear.

Answer 2

I recreated the mail under user rights and now everything seems to work and it became like this:
What is it and how?
Where can I see the full logs?

Answer 3

Some of the boxes have sending and receiving, and some of the boxes have only receiving. Moreover, the same mailbox is used through the mail client (everything is OK) and through gmail (receiving only). How can this be?
What do you advise?